Referral * system, affiliate program, bring a friend?

Question

Partnership programs

Good time of the day, at what time it is desirable to use free CMS, it is possible to implement a customer loyalty program, which is called differently, options in the header. The meaning is as follows: the client is sent a link that he recommends to his friends by email, social networks, instant messengers, .. the link leads to a feedback web form. Everything preferably goes into the database, EXCEL ... well, at worst, email, always with the tag who brought the client. As far as I know, OpenCart has its own regular affiliate program, in Bitrix, maybe someone knows in what other CMS can implement this program, well, or a module, plugin, script ..

Answer 1

Generate a random unique code for each user, then substitute it for his referral link. When another person enters the site using this link, look for who owns this code and prescribe its id to the visitor.